User:Sarah Burkhard/Notebook/471 Nano Notebook/2017/03/21: Difference between revisions

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==Objectives==
==Objectives==
* UV-Vis prepared solutions
* UV-Vis prepared solutions
* Prepare ~ 50mM His solution
[[Image:Screenshot 2017-03-21 at 2.03.24 PM.png]]


==Observations==
==Observations==

Revision as of 11:05, 21 March 2017

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Objectives

  • UV-Vis prepared solutions
  • Prepare ~ 50mM His solution

Observations

  • The capped and the non-capped Arg at pH 14 show purple color
  • Cys-Arg 10 times ratio and the 5 times ratio show white precipitate
  • capped pH 8 and 10 show yellow/orange color
  • The non-capped shows a peak at 580 nm. The capped shows a peak at the same wavelength, but with muss less intensity.
  • The Cys-Arg mix absorbs at a wavelength around 370 nm, and shows a shoulder around 240 nm.
  • The capped pH

Discussion

The yellow color from the capped Arg may come from a reaction of the N-cap, which has a carboxamide group. Yellow in specific often indicates amino groups (N=O) . This could be further confirmed using IR spectroscopy.

Further, the fact that NPs formed above pK2, where the amino acid is negatively charged (above pH 13.2) , leads us to run further tests with Histidine, which has a lower pK2 and therefore a wider range of pH we can test.

Histidine will have a negative one charge at pH above 8.97.

pKa1 1.78 (carboxylic group will be protonated only at pH below 1.78 )

pKa2 8.97 (amine will be protonated only at pH values below 8.97 )

pKaR 5.97 (amine in R chain will be protonated at pH values below 5.97)

charges:

below 1.78: charge is 2+

1.78 - 5.97 : +1

5.97 - 8.97 : 0

above 8.97  : -1


We will run Histidine at pH 7 , 10, 12, and 14 .




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